The major objective of the project is to identify the host factors associated with resistance to dental caries. Adults with no history of dental caries, despite environmental challenge, will serve as the focus for comparative studies with matched subjects with high caries activity. Separately collected salivary secretions, pellicle and plaque will be examined in the two groups for factors that can modify: (1) bacterial adherence, growth, and acid production and (2) the ability of the generated acid to produce demineralization. Parameters to be examined will include: (a) direct antibacterial factors, such as SigA antibody levels against specific components of cariogenic bacteria, lysozyme, lactoferrin and lactoperoxidase (amount and antibacterial activity), (b) aggregation potential using laser light to measure rate, (c) amount and nature of acids and bases produced in plaque, employing a recently modified system of liquid column partition chromatography. Salivary factors already identified as differing in the two groups (albumin binding fraction and "extra" precipitin bands) will be characterized and quantitated in saliva, pellicle and plaque. The concentration of specific phosphoproteins and cationic proteins will be compared and their protective properties assayed in an in vitro system (in collaborative studies).